This invention relates in general to magnet assemblies and magnets contained therein, and particularly to loudspeakers having a magnet system that achieves a greater flux within the air gap wherein the voice coil is suspended and reduces distortion.
Conventional loud speakers utilize standard ferrous magnets in conjunction with a voice coil to control the speaker cone, dome, or other diaphragm. However, such magnets are relatively large and heavy and produce stray magnetic fields which require bulky shielding to contain leakage or increased distance therebetween and unnecessarily increase both the size and weight of the loud speaker. Furthermore, the larger components utilized in such transducers produces time displacement distortion and results in slow and inaccurate low frequency reproduction.
It is desirable in loud speakers to have a sub-compact assembly. It has been found that such a sub-compact design can be achieved by utilizing high energy magnets, such as magnets formed of neodymium-iron-boron in place of the standard ferrous magnets. However, even with the use of the neodymium-iron-boron magnets in a conventional topology, assemblies of the drive units are still bulky and complicated requiring numerous parts and numerous steps to assemble. In addition, the prior art magnet assemblies fail to provide a magnet assembly arrangement that is configured to produce a high degree of efficiency in the conversion of an electrical current into a mechanical movement in combination with the magnetic flux produced.
For example, U.S. Pat. No. 5,070,530 to Grodinsky et al. discloses a loudspeaker wherein large ceramic magnets are utilized. In order to decrease the undesirable eddy currents produced by such an arrangement, the ceramic magnet is slotted which may function as a stabilizing means for reducing distortion caused by the signal related magnetic fields induced into the magnet. Such ceramic magnets are by necessity larger in size and require bulkier shielding which may undesirably reintroduce the energy back into the voice coil and may interfere with the magnetic field, thereby leading to distortion.
U.S. Pat. No. 4,868,882 to Ziegenberg et al. discloses a loudspeaker wherein in an attempt to achieve less distortion in lower frequency sound production, an annular coil is provided with a core of amorphous metal. However, the extra materials used with the voice coil may result in the reduced ability to track the rapid changes in audio signals because of the frequency loss as a result of the flattened loudspeaker impedance.
U.S. Pat. No. 5,687,248 to Yen et al. discloses a cup shaped yoke having a first magnet and a second thinner magnet having a plate therebetween wherein similar poles of the magnets are in proximal relation to the plate. The second thinner magnet repels the first magnet and may reduce magnetic leakage. However, the top magnet may itself leak and providing a second plate thereon does not fully eliminate the same. In addition, the second plate on the second magnet does not contribute to the magnetic flux density in the air gap and does not contribute to the production of optimal sound.
U.S. Pat. No. 5,214,710 to Ziegenberg et al. discloses a first ring magnet and a second ring magnet having a plate therebetween whereby similar poles of the magnets are in proximal relation to each other. The second ring magnet repels the first magnet and may reduce magnetic leakage. However, the top magnet may itself leak and the absence of a second plate thereon will fail to prevent leakage. In addition, a second voice coil is included within inner void of the first and second ring magnets thus requiring further materials and a more complex construction.
U.S. Pat. No. 5,740,265 to Shirakawa discloses a transducer having a first and second disk magnets whereby dual magnetic gaps are formed between the outer diameter of the magnets and the same wall forming the yoke. Accordingly, the use of the same yoke to produce the two magnetic gaps may result in distortion as a result of the leakage of magnetic flux. In addition, the need for a longer coil bobbin adds to the size of the magnet structure and may result in lower quality sound production.
Therefore, there remains a long standing and continuing need for an advance in the art of loudspeakers that is simpler in both design and use, is more economical, compact, and efficient in its construction and use, and can quickly be assembled while eliminating the need for larger magnets.
Accordingly, it is a general object of the present invention to overcome the disadvantages of the prior art.
It is another object of the invention to provide a loudspeaker wherein the magnet assembly is reduced in size.
It is another object of the present invention to provide a loudspeaker wherein the assembly is reduced in weight.
It is another object of the present invention to provide a loudspeaker wherein the magnets and their housing is relatively compact.
It is yet another object of the present invention to provide a loudspeaker wherein the magnet structure produces a more efficient magnetic flux resulting in an increased motor strength and improved sound quality.
It is yet another object of the present invention to provide a loud speaker wherein the magnet structure produces less leakage of the magnetic flux.
It is yet another object of the present invention to provide a loudspeaker that provides lower distortion between the frequencies of 100 to 1000 Hz.
In keeping with the principles of the present invention, a unique loudspeaker utilizing a novel magnetic assembly is presented which overcomes the shortfall of the prior art. The magnet assembly has a preferably circular first seat that has a peripheral annular wall that extends perpendicularly therefrom. First seat is a magnet pot and is preferably constructed of low carbon steel. A first magnet that is preferably annular is received within the wall of first seat to form a uniform channel between and outer edge of the first magnet and the wall. A first aperture is axially defined within said first magnet. First magnet is attached to the floor of the first seat by any adhesive means that is known in the art such as, but not limited to, structural adhesives.
A plate that is preferably annular is positioned upon the first magnet. The plate also has an aperture axially defined therethrough and in substantial alignment with the aperture of the first magnet. An annular lip extends inwardly from a top portion of the wall such that an annular gap is created between the lip and the plate. An annular flange extends outwardly from the top portion of the wall and is adapted to receive a chassis thereon.
A second magnet that is preferably annular is positioned over the plate and also has an axially defined aperture therein. The second magnet is positioned such that the similar polarities of the first and second magnet are in proximal relation. In addition, the aperture defined through the second magnet, the plate, and the first magnet are substantially aligned.
A yoke having a planar region and a protruding region is positioned over the second magnet such that the protruding region extends through the aperture and connects to the seat. In such an arrangement, a first magnetic flux is created and maintained by the first magnet, plate, gap, annular lip, wall and the seat. In addition, a second magnetic flux is created and maintained by the second magnet, plate, gap, annular lip, wall, seat, the protruding region, and the planar region. The increased magnetic flux is directed into the gap wherein a voice coil is moveably suspended.
An annular chassis is positioned over the flange and the chassis moveably maintains a generally conical diaphragm thereon. The voice coil is attached to the conical diaphragm by a bobbin. As current is applied to the voice coil, the voice coil is forced to move within the gap due to the magnetic flux created by the magnets and other components. Accordingly, the conical diaphragm moves back and forth and thereby generates audio output.
Such stated objects and advantages of the invention are only examples and should not be construed as limiting this invention. These and other objects, features, aspects, and advantages of the invention herein will become more apparent from the following detailed description of the embodiments of the invention when taken in conjunction with the accompanying drawings and the claims that follow.